What is the clinical evidence from this study?

Study design: Cohort. Population: Implantable cardioverter-defibrillator (ICD) patients (n=605). Intervention: Largest T-wave loop area (4th quartile) vs. Smaller T-wave loop area (1st-3rd quartiles). Primary outcome: First appropriate ICD shock (HR 0.59, 95% CI 0.35-0.99, p=0.044).

March 14, 2017Open Access

T-wave loop area from a pre-implant 12-lead ECG is associated with appropriate ICD shocks

Key Result

A larger T-wave loop area on pre-implant 12-lead ECG was independently associated with a reduced risk of appropriate ICD shocks (HR 0.59).

Study Design

Type

Cohort (n=605)

Multicenter

Structured PICO

Does pre-implant T-wave loop area and circularity predict appropriate ICD shocks in patients receiving an ICD?

Population

605 patients undergoing implantable cardioverter-defibrillator (ICD) or cardiac resynchronization defibrillator implantation for guideline-recommended indications, mean age 65, 82% male, Germany-based. Key characteristics: 68% ischemic cardiomyopathy, 72% primary prevention, mean LVEF 28±10%.

Intervention

Pre-implantation 12-lead ECG assessment of T-wave loop area (TLA) and T-wave loop circularity (TLC)

Comparator

Patients with different quartiles of TLA and TLC (e.g., highest quartile vs remaining cases)

Outcome

All-cause mortality and first appropriate ICD shock (shock for ventricular tachycardia or fibrillation) over average 3.8±1.4 years follow-uphard clinical

Pre-implantation ECG assessment of T-wave loop area and circularity can independently predict the risk of appropriate ICD shocks, potentially aiding in patient selection for ICD therapy.

Main Result

Effect estimate: HR 0.59 (95% CI 0.35-0.99)

Absolute Event Rate: 13% vs 23%

p-value: p=0.044

Limitations

Retrospective data analysis
Only approximately 50% of the total cohort had an analyzable digital ECG
Factors like LV remodeling over time resulting in changes in propensity for arrhythmia are not reflected
ICD programming could not have been uniform over the 7-year enrollment period
Anti-tachycardia pacing was not considered as an endpoint and might have influenced the occurrence of ICD shocks

Abstract

AIMS: In implantable cardioverter-defibrillator (ICD) patients, predictors of ICD shocks and mortality are needed to improve patient selection. Electrocardiographic (ECG) markers are simple to obtain and have been demonstrated to predict mortality. We aimed to assess the association of T-wave loop area and circularity with ICD shocks. METHODS: The study investigated patients with ICDs implanted between 1998 and 2010 for whom digital 12-lead ECGs (Schiller CS200 ECG-Network) of sufficient quality were obtained within 1 month prior to the implantation. T-wave loop area and circularity were calculated. Follow-up data of appropriate shocks were obtained during ICD clinic visits that included reviews of device stored electrograms. RESULTS: A total of 605 patients (82% males) were included; 68% had ischemic cardiomyopathy and 72% were treated for primary prevention. Over 3.8±1.4 years of follow-up, 114 patients (19%) experienced appropriate shock(s). Those with smaller T-wave loop area received fewer shocks (TLA, hazard ratio, HR, per increase of 1 technical unit, 0.71; 95% confidence interval, 0.53-0.94; P = 0.02) and those with larger T-wave loop circularity (TLC) representing rounder T wave loop received more shocks (HR per 1% TLC increase 2.96; 0.85-10.36; P = 0.09). When the quartile containing the largest TLA and TLC values, respectively, were compared to the remaining cases, TLA remained significantly associated with fewer and TLC with more frequent shocks also after multivariate adjustment for clinical variables (HR, 0.59 0.35-0.99, P = 0.044; and 1.64 1.08-2.49, P = 0.021, respectively). CONCLUSIONS: The size and shape of the T-wave loop calculated from pre-implantation 12-lead ECGs are associated with appropriate ICD shocks.

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